The present invention pertains to a seat belt actuator/retarder for absorbing energy and controlling seat belt payout during an impact or high levels of acceleration imposed on the belt wearer in a vehicle.
In the application of seat belts and so-called shoulder belts in vehicles, the sudden acceleration of and energy transferred to the belt wearer in the event of a vehicle collision or extreme deceleration is typically absorbed by the belt material and some deflection of the belt retractor mechanism. When vehicle seat and shoulder belts are used in conjunction with inflatable xe2x80x9cairbagsxe2x80x9d or so-called supplemental restraint systems, it is desirable to also prevent the belt wearer from moving forward toward the airbag until the bag has had an opportunity to deploy fully so as to minimize injurious impact forces.
The energy of the impact during a collision or other forms of extreme deceleration is transferred from the vehicle occupant to the seat belt, and this energy in conjunction with the deployment of an airbag-type restraint can injure such occupant. Accordingly, it is desirable to minimize such impact by varying the rate of the so-called payout of the belt system thereby slowing down forward movement of the belt wearer toward the vehicle steering column, dashboard or instrument panel in order to minimize injury caused by the belt (seat and/or shoulder) and to allow the airbag to fully deploy, thus minimizing impact forces on the vehicle occupant.
The aforementioned problem is aggravated when shorter and lighter weight occupants occupy the vehicle since such persons are normally seated closer to the steering wheel or control column, in the case of the vehicle driver, when an airbag type restraint deploys. Accordingly, such vehicle occupants have less distance to travel toward the steering wheel or control column so they tend to impact an airbag type restraint when it is in the initial phase of inflation.
Therefore, it has been deemed desirable to provide an energy absorption mechanism which may be operably connected to or form part of a seat and/or shoulder belt retractor mechanism to control the restraining forces and/or so-called unreeling or payout of the belt to minimize injury to the belt wearer. It is to these ends that the present invention has been developed.
The present invention provides an actuator which is operable to control or retard the unreeling or payout of a seat belt, so-called shoulder belt or similar restraint worn by an occupant of a vehicle to minimize injury to the occupant in the event of a collision or other event which causes extreme deceleration of the vehicle.
In accordance with one aspect of the present invention, an actuator is provided which includes mechanism responsive to a magnetorheological fluid acting on the mechanism in such a way that the payout or restraining forces acting on the belt or similar restraint may be selectively varied during a collision or rapid deceleration of a vehicle so as to minimize injury to the belt wearer in the vehicle. The actuator includes mechanism for generating a magnetic field to act on a magnetorheological fluid to control the shear properties of the fluid and thereby effect operation of the actuator mechanism to selectively control the payout of or retarding forces acting on the belt or a similar restraint device. The magnetic field may be controlled in relation to sensing the weight of the occupant wearing the belt and in relation to sensing the deceleration of the vehicle due to a collision or other event.
The belt actuator of the present invention may be operably connected to a conventional seat belt retractor mechanism or configured to be drivably connected to a belt retractor reel and form part of the belt retractor per se.
In one embodiment of the invention a rotatable shaft operably connected to the seat belt retractor reel drives a piston to displace a magnetorheological fluid through a magnetic field formed by an electric coil, the magnetic field extending transversely across a restricted flow path for the magnetorheological fluid. The intensity of the magnetic field may be selectively varied in accordance with certain control parameters including parameters associated with the belt wearer""s weight and the intensity of the collision or other event which causes rapid deceleration of the vehicle.
In another embodiment, the invention includes a multi-plate clutch or disc-type brake mechanism in which a magnetorheological fluid is disposed between adjacent plates or discs and a magnetic field may be imposed on the fluid by a coil disposed adjacent the plates. Relative rotation of alternate ones of the plates or discs may be controlled in relation to the rotative speed of the belt retractor reel by a speed increasing planetary type gearset, for example.
The present invention still further contemplates an embodiment of a magnetorheological seat belt actuator or retarder which comprises a stator or core member supporting an electromagnetic coil over which is sleeved an annular, somewhat cylindrical can-shaped rotor which is drivably connected to the seat belt retractor or may form part of the seat belt retractor reel. An annular space between the stator and the rotor is filled with a magnetorheological fluid whose shear properties may be varied by an electrical signal imposed on the coil to selectively vary the forces required to rotate the rotor and thus the rate of payout of a belt or similar restraint device connected to the actuator.
Those skilled in the art will further appreciate the above-mentioned advantages and superior features of the restraint belt actuator or retarder of the invention upon reading the detailed description which follows in conjunction with the drawings.